3P-Cholestanol

The relative reactivity of primary and secondary positions adjacent to oxygen can be strongly dependent on the nature of the oxidant. For example, treatment of the methyl ethers (8) and (10) with chromium trioxide in acetic acid leads to the formation of the formates (9) and (11), respectively (equations 13 and 14). In direct contrast, n-decyl methyl ether is oxidized exclusively to methyl n-decanoate (83% yield) by ruthenium tetroxide (equation 11). Under similar reaction conditions, 3p-cholestanol methyl ether gives cholestan-3-one as the major product, together with traces of the corresponding formate. Therefore, at least in the case of ruthenium tetroxide, primary positions appear to be more reactive than tertiary. 

This selectivity for axial alcohol oxidation is not, apparently, universal since both the 3a- (18) and the 3P-cholestanol (19) are oxidized to cholestanone (20) with a better yield obtained on oxidation of the equatorial, 3p-alcohol (Eqn. 21.31). Selectivity in the platinum catalyzed oxidation of steroid alcohols. 

The important drop in the yields from primary to secondary alcohols was attributed in part to a competing trifluoroacetylation induced by the presence of phenyl trifluoroacetate, a decomposition product of the reagent (6). Reaction of 3p-cholestanol (77) with (6) led the 0-phenyl ether (78) in 29% yield, together with 3P-cholestanyl trifluoroacetate (79) in 65% yield. 

The reaction of triphenylbismuth diacetate (47) with secondary alcohols under neutral conditions resulted in poor to moderate yields of the corresponding 0-phenyl ethers 2-propanol gave about 20% of the 0-phenyl ether with a large excess of the dcohol, cyclohexanol less than 3% and 3p-cholestanol gave 36% of the 0-phenyl ether. Moreover, no reaction was observed between triphenylbismuth diacetate and primary alcohols.53-55... 

Stereospeciflc Conversion of Alcohols to Azides. Reaction of an alcohol with DPPA, Triphenylphosphine, and Diethyl Azodi-carboxylate forms the corresponding azides in 60-90% yields. The stereospeciflc nature of this reaction permits the conversion of A -sterols such as 3p-cholestanol exclusively to the 3a-cholestanyl azide in 75% yield. This synthesis is clearly superior to the alcohol - tosylate -> azide route which is longer and also prone to competing elimination reactions. 

Examination of Cribrlcelltna crlbraria from New Zealand has revealed that it contained a range of sterols as well as alkaloids (see Section 2.3.4). While the authors stated that twelve of the sterols were Identified, only nine were actually named in the publication - cholesterol, 25, 24-methylcholesta-5,22-dien-3P-ol, 26, cholestanol, 27, cholest-4-en-3-one, 28, cholesta-5,22-dien-3P-ol, 29, 24-ethylcho-lesterol, 30, 24-methylenecholesterol, 31, 24-ethylcholesta-5,22-dien-3p-ol, 32, 24-methyl-26,27-blsnorcholesta-5,22-dien-3p-ol, 33, (20). 

This rare, lipid storage disease, which was first described in 1937, is characterized clinically by the presence of xanthomas or lipid deposits of cholesterol and cholestanol (5a-cholestan-3p-ol) in the brain and tendons. 

Cholestadien-3-P-ol. See 7-Dehydrocholesterol Cholecalciferol Cholestanol Cholestan-3-ol Cholestan-3-ol, (3p,5a)- Cholestan-3p-ol 5o-Cholestanol 5a-Cholestan-3P-ol. See Dihydrocholesterol Cholestan-3-ol, 2-octyldecanoate. See Dihydrocholesteryl octyidecanoate Cholest-5-ene-3p-yl nonanoate. See Cholesteryl... 

Cholestanol Sa-cholestan-3P-ol, a zoosterol (see Sterols). It is a 5,6-dihydro-derivative of cholesterol, and occurs in small amounts with cholesterol in animal cells. In some sponges, C. is the main sterol. It differs from the stereoisomeric Coprostanol (see) in the configuration at CS and the trans configuration of rings A and B. 

In addition to A -3p-hydroxy-sterols Stellata clarella also contains 5a-cholestanol (147), 5a-ergostanol (256), and 5a-poriferastanol (257). The latter two must be counted as new to Porifera. 

---